Keystone



FIG. 1 is a perspective view of the keystone showing the new design in use with vinyl siding and located above a window on a residence;

FIG. 2 is a top plan view shown on an enlarged scale thereof;

FIG. 3 is a front elevation view shown on an enlarged scale thereof;

FIG. 4 is a left side view shown on an enlarged scale thereof;

FIG. 5 is a right side view shown on an enlarged scale thereof;

FIG. 6 is a bottom view shown on an enlarged scale thereof;

FIG. 7 is a rear view shown on an enlarged scale thereof; and,

FIG. 8 is a front view thereof showing on an enlarged scale how distinctive indicia may be placed thereon.

Material shown in dotted lines shows the environment in which the invented design is used, and forms no part of the invented design.

The broken line showing of vinyl siding, a window and distinctive indicia is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a keystone, as shown and described. 